The oil furnace works fine all day and evening, then overnight I have the programmable thermostat lower the temperature at 11pm. But every morning at 5am when the thermostat tries to turn the temperature back up the furnace comes on for 45 seconds and shuts off. I go to the basement take off the panel. The box has a red light flashing. I push the reset button on the box, the furnace starts immediately and runs OK until the next morning. I've also had similar problems 5 or 6 months ago, had to call repairman twice and he said that he replaced almost everything he could replace. And it worked til now.
Have to start the furnace manually every morning
hvac
Best Answer
Something similar happened to my gas boiler. It was a problem with the ignition electronics. Every night, when the thermostat was lowered, the circuit board would cool down and a solder connection would come loose. Sometimes the board could be wiggled to make the connection again. Eventually I opened it up and identified and fixed the loose solder connection.
The ignitor box looked something like this: